The present invention relates to electrostatography and, more particularly, to cleaning brushes for use in electrostatographic imaging apparatus.
In known electrostatographic imaging apparatus, a photoconductive insulating element is typically charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates on the photoconductive element an electrostatic latent image that corresponds to the image contained within the original document. Alternatively, a light beam may be modulated and used to selectively discharge portions of the charged photoconductive surface to record the desired information thereon. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with developer powder referred to in the art as toner. Most development systems employ developer comprising charged carrier particles and charged toner particles that triboelectrically adhere to the carrier particles. During development, the toner particles are attracted from the carrier particles by the charged pattern of the image areas of the photoconductive insulating element to form a powder image thereon. This toner image may be subsequently transferred to a support surface such as copy paper, to which it may be permanently affixed by heating and/or the application of pressure. Usually, all of the developed toner does not transfer to the copy paper, and therefore cleaning of the photoconductive surface is required prior to its entering the next charge and expose cycle.
Commercial embodiments of the apparatus generally described above have taken various forms that entail particular techniques for cleaning the insulating surface of the photoconductive member. One of the most common and commercially successful cleaning techniques has been the use of a cylindrical brush with soft bristles having suitable triboelectric characteristics. The bristles are soft so that, as the brush is rotated in contact with the photoconductive surface to be cleaned, the fibers continually wipe across the surface to produce the desired cleaning without causing significant surface wear or abrasion.
Further developments in cleaning techniques and apparatus, in addition to relying on the physical contacting of the surface to be cleaned to remove the toner particles, also entail establishing electrostatic fields by electrically biasing one or more members of the cleaning system to establish a field between a conductive brush and the insulative imaging surface and thereby cause the toner on the imaging surface to be attracted to the brush by electrostatic forces. Thus, if the toner on the photoreceptor is positively charged, the bias on the brush would be negative. The creation of a sufficient electrostatic field between the brush and imaging surface to achieve the desired cleaning effect is accomplished by applying a DC voltage to the brush. Typical examples of such techniques are described in U.S. Pat. Nos. 3,572,923 and 3,722,018.
U.S. Pat. No. 4,319,831, the disclosure of which is incorporated herein by reference, describes a cleaning brush for a copying device wherein the brush is composed of composite conductive fibers consisting of at least one conductive layer containing conductive fine particles and at least one non-conductive layer in a monofilament. The electrical resistance of the conductive fibers is less than 1015 ohms/cm. The fineness of the fibers is from 3 to 300 denier and the length of the piles is from 3 to 50 mm. The percentage of the outer surface area occupied by the conductive layer is not more than 50%. Conductive carbon black particles may be used with a number of synthetic resins, including polyaraides. Other cleaning brushes containing electroconductive fibers are described in U.S. Pat. Nos. 4,835,807, 5,689,791, and 6,009,301, the disclosures of which are incorporated herein by reference.
The present invention is directed to a cleaning brush for use in an electrostatographic imaging apparatus. The cleaning brush comprises individual fibers provided with a finishing agent comprising a water-miscible aliphatic organic compound containing a plurality of alcoholic hydroxy substituents. The finishing agent is selected from the group of organic compounds having a molecular weight of up to about 250 and polyethylene glycols having a number-average molecular weight of about 1000 to about 200,000.
The present invention is further directed to an improved electrostatographic imaging apparatus that includes a photoconductive imaging element and a cleaning brush. The improvement comprises: the photoconductive imaging element having a photoconductive surface portion comprising a polycarbonate binder resin, and the cleaning brush comprising individual electroconductive fibers provided with a finishing agent comprising a water-miscible aliphatic organic compound containing a plurality of alcoholic hydroxy substituents and having a molecular weight of up to about 250. The finishing agent is selected from among organic compounds having a molecular weight of up to about 250 and polyethylene glycols having a number-average molecular weight of about 1000 to about 200,000. The cleaning brush removes toner from the photoconductive surface portion of said imaging element without damaging it.